DE102023123511A1 - component grinding of cement components - Google Patents

Abstract

The present invention relates to a process for producing a cement from at least two components, characterized in that at least two of the components are ground separately.

Description

The invention relates to a method for the efficient grinding of various components for a cement.

The substitution rate in cement is increasing. The proportion of fired clinker is therefore being reduced. Common substitutes today include unburnt limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash and the like. In order to achieve the specified strength classes, the cements usually have to be ground more finely. This leads to higher energy consumption during grinding. In addition, the different components have different grindabilities, so that the components that are easier to grind are ground much finer than would be necessary. This further increases the energy required for grinding.

Another point to consider is the vibration level of the mill. This can be counteracted with moisture, but this is harmful to the product. It is therefore necessary to maintain the necessary fineness with as little water as possible at a sufficiently low vibration level in the mill.

From the US 2013 / 0040257 A1 A method and an apparatus for cement production is known.

From the EP 3 326 720 B1 A process for the processing of multiphase mineral raw materials is known.

From the EP 2 906 510 B1 A process for producing cement is known.

From the EP 2 980 036 B1 A process for grinding cement clinker is known.

The object of the invention is to provide a grinding process in which all components are ground to the necessary fineness in an energy-efficient manner.

This object is achieved by the method with the features specified in claim 1. Advantageous further developments emerge from the subclaims, the following description and the drawings.

The method according to the invention is used to produce a cement from at least two components. For example, the cement can be a cement classified as CEM I. Clinker is preferably selected as the first component. Clinker, burnt lime, creates an alkaline environment when mixed with water when it sets. The second component can be gypsum, for example, which is used as a sulfate carrier in order to be able to adjust the setting behavior. At least two of the components are ground separately. This allows the first component and the second component to be optimally ground individually, depending on their grindability and the fineness required for the end product. This also allows the component that is more difficult to grind to be ground more finely, for example, without the component that is easier to grind being ground unnecessarily finely and thus wasting unnecessary energy.

In a further embodiment of the invention, the first component is clinker and the second component is selected from the list comprising gypsum, unburnt limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, old cement brick. The clinker substitutes have the advantage that the very high carbon dioxide release (from the lime) during clinker production is avoided, thus emissions can be avoided in a simple manner. In addition, some substances, such as pozzolans, can give the concrete made from the cement advantageous properties, for example in terms of water resistance.

In a further embodiment of the invention, the separate grinding takes place one after the other in the same device. In a vertical roller mill in particular, it is particularly easy to change the material to be ground, so that a quick change simplifies a separate process in just one device, which in turn reduces the investment in the plant.

In a further embodiment of the invention, the second component is ground finer than the first component. Clinker as the first component has a high reactivity, practically all clinker substitutes that can be selected as the second component have a lower reactivity, so that finer grinding is necessary here. Normally, the cement is therefore ground as a mixture, which in turn means that the comparatively easy-to-grind clinker is ground much finer and thus becomes much finer than the third component. The fact that the clinker is separated and only coarsely ground to the necessary fineness saves grinding energy.

In a further embodiment of the invention, the first component is ground to a Blaine fineness of at least 5250 cm ² /g. Preferably, a fineness is produced which does not exceed 6000 cm ² /g, preferably not more than 5750 cm ² /g, particularly preferably not more than 5500 cm ² /g. The fineness of at least 5250 cm ² /g according to Blaine corresponds for clinker to a residue of less than 8% of the particles on a 25 µm sieve.

In a further embodiment of the invention, the second component is ground to a Blaine fineness of at least 6000 cm ² /g. The Blaine fineness of at least 6000 cm ² /g corresponds to a residue of less than 1% of the particles in a 32 µm sieve for granulated blast furnace slag.

In a further embodiment of the invention, clinker and gypsum are ground together.

In a further embodiment of the invention, a fineness of at least 5250 cm ² /g up to 6750 cm ² /g according to Blaine and a residue of less than 8 wt.% residue on the 25 µm sieve during grinding is achieved.

In a further embodiment of the invention, at least a third component is used to produce the cement. The third component is different from the second component and is selected from the list comprising gypsum, unburnt limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, old cement brick. At least two of the components are ground together and at least two of the components are ground separately. For example, the clinker can be ground together with the gypsum (as the third component) and the second component, for example granulated blast furnace slag, can be ground separately, or the gypsum and the second component, for example granulated blast furnace slag, can be ground together and the clinker separately, or the clinker and the gypsum can be ground together and the second component, for example granulated blast furnace slag, and the gypsum can also be ground together separately. This means that all components are not mixed and ground together in a common grinding step, as is currently the case. This makes it possible to specifically take into account the different grindability of the clinker and the second component in particular. In particular, the clinker substitutes that are chosen as the second component usually require a lower fineness than the clinker. At the same time, they have a lower grindability, so that when they are ground together, the more easily grindable material is over-ground, resulting in excessive energy consumption.

In a further embodiment of the invention, size-selective separation takes place after grinding. The coarse fraction is returned to the mill, the fine fraction is removed as product. This opens up the possibility of using mills that cannot immediately achieve the necessary fineness for the entire material to be ground.

For a vertical roller mill, a classifier has proven to be particularly suitable for size-selective separation, as the material to be ground is carried out of the vertical roller mill in a gas stream and can thus be fed directly to a classifier. Preferably, the classifier only separates the coarse fraction. The fine fraction is then separated from the gas stream in a dust filter, for example.

In a further embodiment of the invention, a vertical roller mill is selected for grinding. The vertical roller mill achieves the required fineness in an energy-efficient manner with a high throughput and can also be switched between different grinding materials relatively quickly and easily.

In a further embodiment of the invention, a combination of a material bed roller mill and a ball mill is used for grinding. Preferably, a size-selective separation is used here, which produces a coarse fraction, a medium fraction and a fine fraction. For example, this can be a sifter. The material input stream is fed to the size-selective separation device and the coarse fraction is fed to the material bed roller mill. The material comminuted in the material bed roller mill is fed back to the material input stream. The medium fraction is fed from the size-selective separation device to the ball mill and further comminuted there. The material ground in the ball mill is fed back to the size-selective separation device. The fine fraction is either removed as a product or passed through a second size-selective separation device, with the second coarse fraction being fed to the ball mill. This makes it easy to achieve higher finenesses.

• 1 erstes Beispiel
• 2 zweites Beispiel

The method according to the invention is explained in more detail below with reference to embodiments shown in the drawings.

• 1 first example
• 2 second example

In 1 a first exemplary device for carrying out the method according to the invention is shown. A clinker gypsum or a mixture of activated clay and gypsum is fed to a vertical roller mill 21 via the material feed 10. The vertical roller mill is then Gas is supplied via a gas supply 12. As a result, the light, ground material is discharged with the gas stream and fed to a size-selective separation device 30, which can also be arranged in a housing with the vertical roller mill 21. There, separation takes place into a coarse fraction 32, which is fed back to the vertical roller mill, and a fine fraction, which is fed into a dust separator 40 to separate solids and gas. The gas is discharged via the gas outlet 44 and can theoretically be returned to the gas inlet 12. The finished product is removed via the product outlet 42. The cement can be produced by separate grinding, with all components having the optimal fineness and no component being ground too finely, so that the energy requirement for grinding is optimized.

2 shows a second exemplary device for carrying out the method according to the invention. Via the material feed 10, a clinker gypsum or a mixture of activated clay and gypsum is temporarily fed to a size-selective separation device 34, which divides the material into a fine fraction 31, a medium fraction 33 and a coarse fraction 32. The coarse fraction 32 is fed to a material bed roller mill 22 and crushed there. The ground material 25 is fed to the material feed 10 and thus to the renewed size-selective separation. The medium fraction 33 is fed to a ball mill 23 and the ground material 25 from the ball mill 23 is fed back to the size-selective separation device 34. The fine fraction is fed to a second size-selective separation device 35, the second coarse fraction 36 from the second size-selective separation device 35 is added to the medium fraction 33 and fed to the ball mill 23. The fine fraction of the second size-selective separation device 35 is fed to a dust separator 40, the gas is discharged via the gas outlet 44 and the product is removed via the product outlet 42.

reference sign

10

material supply

12

gas supply

21

vertical roller mill

22

high-pressure roller mill

23

ball mill

25

ground material

30

size-selective separator

31

fine fraction

32

coarse fraction

33

middle fraction

34

size-selective separator

35

second size-selective separator

36

second coarse fraction

40

dust collector

42

product outlet

44

gas outlet

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• US 2013 / 0040257 A1 [0004]
• EP 3 326 720 B1 [0005]
• EP 2 906 510 B1 [0006]
• EP 2 980 036 B1 [0007]

Claims (12)

Process for producing a cement from at least three components, characterized in that at least two of the components are ground together and at least two of the components are ground separately. procedure according to claim 1 , characterized in that the first component is clinker, the second component being selected from the list comprising gypsum, unburnt limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, old cement brick. Method according to one of the preceding claims, characterized in that the separate grinding takes place one after the other in the same device. Method according to one of the preceding claims, characterized in that the second component is ground finer than the first component. Process according to one of the preceding claims, characterized in that the first component is ground to a fineness of at least 5250 cm ² /g according to Blaine. Process according to one of the preceding claims, characterized in that the second component is ground to a fineness of at least 6000 cm ² /g according to Blaine. Method according to one of the preceding claims, characterized in that clinker and gypsum are ground together. Process according to one of the preceding claims, characterized in that a fineness of at least 5250 cm ² /g up to 6750 cm ² /g according to Blaine and a residue of less than 8 wt.% residue on the 25 µm sieve is achieved during grinding. Method according to one of the preceding claims, characterized in that at least a third component is used to produce the cement, wherein the third component is different from the second component and is selected from the list comprising gypsum, unburnt limestone, calcined clays, pozzolans, granulated blast furnace slag, steel slag, fly ash, old concrete, old cement brick, wherein at least two of the components are ground together and at least two of the components are ground separately. Method according to one of the preceding claims, characterized in that after grinding, a size-selective separation takes place, the coarse fraction (32) being returned to the mill, the fine fraction (31) being removed as product. Method according to one of the preceding claims, characterized in that a vertical roller mill (21) is selected for grinding. Method according to one of the Claims 1 until 10 , characterized in that a combination of a material bed roller mill (22) and a ball mill (23) is used for grinding.

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